Three-dimensional semiconductor mounting has become essential for further higher density, higher capacity, higher speed, and low power consumption. A three-dimensional semiconductor mounting technique is a semiconductor production technique for thinning a semiconductor chip, and connecting the chip to another chip using a through silicon via (TSV) to form a multilayer. In order to realize this technique, a step of grinding a non-circuit-formed surface (also referred to as “back surface”) of a substrate on which a semiconductor circuit has been formed to thin the substrate, and forming an electrode including a TSV on the back surface is required.
Conventionally, in the step of grinding a back surface of a silicon substrate, a protective tape is attached to a surface opposite to a surface to be ground to prevent breakage of a wafer during grinding. However, this tape uses an organic resin film as a base material, which has flexibility, but inadequate strength and heat resistance. Therefore, the tape is not suited to the steps of forming a TSV and forming a wiring layer on the back surface.
For this reason, a system has been proposed in which a semiconductor substrate is bonded to a support (supporting substrate) of silicon, glass, or the like, through an adhesive layer to sufficiently withstand the steps of grinding a back surface and forming a TSV and an electrode on the back surface. In this system, the adhesive layer used in bonding the substrate to the support is important. The adhesive layer requires sufficient durability to bond the substrate to the support without gaps and withstand a subsequent step. Further, it is necessary that a thin wafer be easily delaminated from the support finally. The adhesive layer is referred herein to as “temporary adhesive layer” since it is finally delaminated.
As known temporary adhesive layer and method for delaminating the layer, a technique in which a silicone pressure sensitive adhesive is used for a temporary adhesive layer (Patent Literature 1), and a technique in which bonding and delaminating is carried out using a heat-melting hydrocarbon-based compound for an adhesive material in a heat molten state (Patent Literature 2) have been proposed. In the former technique, a substrate is bonded to a support using an addition-curable silicone pressure sensitive adhesive, and during delaminating, the substrate is immersed in a chemical agent which is capable of dissolving or decomposing a silicone resin, and then detached from the support. This technique requires a very long time for delaminating, so that application of this technique to an actual production process is difficult. The latter technique is simple because of control only by heating, but does not have sufficient heat stability at a high temperature higher than 200° C. Therefore, the applicable range is narrow.
Further, a technique in which an adhesive containing a light-absorbing substance is irradiated with high-intensity light to decompose a temporary adhesive layer, thereby delaminating a thin wafer from a support (Patent Literature 3), and a technique in which a combination of an adhesive containing a light-absorbing substance and an adhesive containing a styrene base elastomer is irradiated with high-intensity light, and the elastomer is then swollen by a solvent so as to be delaminated (Patent Literature 4) have been proposed. However, both the techniques require an expensive apparatus such as a laser, and suffer from a problem in which a processing time per substrate is extended, and particularly in the latter technique, the processing time is further extended due to the solvent treatment.